Stable extract of hypericum perforatum L., a method for producing the same, and corresponding pharmaceutical preparations

ABSTRACT

Disclosed is an improved extract of  Hypericum perforatum  L. (St. John&#39;s wort) containing Hyperforin, in which the Hyperforin is stabilized against decomposition or degradation by means of a stabilizer.

It is proved by pharmacological and clinical trials that extracts of St.John's wort (extracts of Hypericum) can be successfully used in case oflight to moderately severe depressions. The mild anti-depressive overalleffect could not be exactly assigned to one or several components; cf.J. Hölzl, S. Sattler and H. Schütt, Johanniskraut: Eine Alternative zusynthetischen Antidepressiva (St. Johns wort: an alternative tosynthetic antidepressants), Pharmazeutische Zeitung, No. 46, 139.Jahrgang, 17. November 1994, pages 3959-3977 and E. Steinegger and R.Hänsel, Pharmakognosie, 5^(th) edition 1992, pages 672-674, SpringerVerlag. However, recently there are stronger hints that Hyperforinprovides a considerable contribution to achieve effectiveness (EP-A-0599 307).

The crude herbal drug consists of the aerial parts of Hypericumperforatum L. The components of Hypericum perforatum L. are among othersHypericin and Hyperforin; cf. J. Hölzl et al., see above.

The preparation of extracts of Hypericum with an enriched content ofHypericin is described in DE-PS- 1 569 849 as well as in S. Niesel andH. Schilcher in Arch. Pharm., Vol. 323 (1990), page 755.

From R. Berghöfer and J. Hölzl , Deutsche Apothekerzeitung, Vol. 126,No. 47 (1986) pages 2569-2573, it is known that Hyperforin in extractsfrom stored crude herbal drugs is already completely degraded after oneweek whilst it should be more stable in the extract of fresh plants.These authors assume that fresh plants contain a stabilizer forHyperforin.

J. Hölzl et al., Planta Med., Vol. 55 (1989) pages 601-602 report aboutHypericum oil and assume a correlation between the concentration ofHypericin and the peroxide value. Hypericum oil products exposed to thesun light show different peroxide values. But according to J. Hölzl etal., there is no relation between the peroxide value and theconcentration of Hypericin.

P. Maisenbacher and K. -A. Kovar report in Planta Med., Vol. 58, (1992),pages 351 to 354 about the stability of Hypericum oil. This oil alsocontained Hyperforin which was degraded within a few weeks.

From EP-A- 0 599 307 primary extracts of the crude herbal drug of St.John's wort (see examples 1-3) are known. These primary extracts areobtained by simply extracting the crude herbal drug with 96% and 60%aqueous ethanol, respectively without any precautionary measures andwithout any additions.

In example 1 the Hyperforin content of the [fresh] primary extract isstated to be 6.3%. In the two other examples no Hyperforin content isstated at all. We have found that such Hyperforin extracts are extremelyunstable; see description, example 5, Table I. The primary extractobtained according to example 1 (comparison) by extraction of the drugwith 70% aqueous ethanol contains after 13 weeks no longer anydetectable amounts of Hyperforin.

Furthermore, it is known to prepare Hypericum oil (oil of St. John'swort; Oleum hyperici) by extraction of crushed (mashed) fresh flowers ofSt. John's wort with a fatty oil such as olive oil, soya-bean oil, wheatgerm oil or sunflower seed oil. Hypericum oil contains variable amountsof Hyperforin and is useful for the topical treatment of wounds, inparticular burns and abrasion; cf. P. Maisenbacher and K. -A. Kovar,Planta Med., Vol. 58 (1992), pages 351-354 and J. Hölzl, L. Demisch andS. Stock, Planta Med., Vol. 55 (1989), pages 601-602.

As well in the drug as in conventional extracts of Hypericum the contentof Hyperforin decreases dramatically until the disappearance of thesubstance within a few months on conventional storage; cf. Ph.D. thesisof P. Maisenbacher, Tübingen 1991 and the Ph.D. thesis of R. Berghöfer,Marburg/L. 1987. In earlier experiments with oily extracts of Hypericumthe stability of compositions containing Hyperforin could only beimproved in a better way by storage under Argon; cf. Ph.D. thesis of P.Maisenbacher, see above. A stabilisation with anti-oxidants such asbutylhydroxytoluene (BHT) and butylhydroxyanisole (BHA) was not achievedin these extracts. Moreover, conventional anti-oxidants such as OxynexLM and Oxynex 2004 do also not improve the stability. In case ofHypericum oil the best stability is achieved (according to P.Maisenbacher's Ph.D. thesis) by use of octyldodecanol (Eutanol G) as anextraction agent. On pages 154-155 Maisenbacher describes historicalmethods of preparation. The crude herbal drug is extracted with hotplant oil, sometimes under the addition of oil of turpentine. Also inthis case Maisenbacher observed degradation, in particular under theinfluence of water. On pages 158-166 Maisenbacher describes theconditions for an optimal process of preparation. The followinginstructions are particularly revealing: water has to be kept out;Eutanol G should be used as extraction agent; conventional anti-oxidantsprovide now protection against oxidation. After an induction period of 3weeks a steady degradation of the Hyperforines began for the olive oilextract; cf. FIGS. 7-10. Despite rinsing with inert gas a completedegradation occurred after 3 months; cf. page 160. The oil prepared bythe use of Eutanol G is stable for half a year at ambient temperatureunder argon. At 30° C. slow degradation occurs; cf. page 161.

Extracts of Hypericum containing Hyperforin can be prepared withpharmaceutically conventional inorganic or organic solvents or mixturesthereof (P. List and P. C. Schmidt, Technologie pflanzlicherArzneizubereitungen, Wissensch. Verlagsgesellschaft mbH, Stuttgart,1984).

Conventional aqueous ethanolic extracts of Hypericum and finishedpharmaceutical compositions prepared thereof usually contain less thanabout 1% Hyperforin (based on the extract). After the storage the valueobviously decreases and moves towards zero depending on the individualstorage conditions. One assumes that processes of oxidation areresponsible for the degradation of the Hyperforin in the crude herbaldrug and the extract.

The technical problem of the present invention is to provideHyperforin-containing stabilized extracts of Hypericum perforatum L. (StJohn's wort) in which the Hyperforin remains stable. It is a furthertechnical problem of the invention to provide a process for thepreparation of these stabilized extracts as well as to providepharmaceutical compositions containing these stabilized extracts inwhich the Hyperforin content also remains stable.

According to the present invention these technical problems are solvedby extracts according to claims 1 to 8, by the process according toclaims 9 to 21 as well as by the pharmaceutical composition according toclaim 22.

The present invention is based inter alia on the unexpected result thatan extract of Hypericum with certain anti-oxidant and/or oxygen bindingstabilizers and reducing agents, which are able to degrade oxidants suchas radicals, peroxides, atmospheric oxygen etc. in the extract and/or toinhibit the degradation of Hyperforin, and optionally carrying out theextraction under inert gas such as nitrogen and/or exclusion of lightand/or with a solvent with a highly reduced oxygen content, is morestable than an untreated extract of Hypericum. This extract can bederived contrary to the obsevations made by R. Berghöfer and J. Hölzl(see above) from a dried and stored crude herbal drug.

A solvent with a highly reduced oxygen content can be prepared byphysical treatment such as rinsing with an inert gas such as nitrogen.In case the extract of Hypericum is preserved or stabilized according tothe present invention, in particular by addition of an anti-oxidant andoptionally by exclusion of light and atmospheric oxygen, then theHyperforin in this extract remains essentially stable. The protectionagainst light and atmospheric oxygen can also be achieved by acorresponding pharmaceutical formulation.

In a preferred embodiment of the process of the present invention forthe preparation of the stabilized extract the fresh or preferably drieddrug of St. John's wort is extracted with aqueous ethanol, the oxygencontent of which was highly reduced by physical treatment. To theextract solution an anti-oxidant agent as a stabilizer is added anddissolved therein because of possibly present oxidants. Further examplesfor preferred solvents for the extraction of St. John's wort compriseaqueous methanol, alkanes with low boiling points having about 5 to 8carbon atoms such as pentanes, hexanes and heptanes, in particularn-heptane, and liquid or supercritical carbon dioxide. The term “aqueousmethanol or ethanol” denotes methanol or ethanol having a water contentof preferably up to about 40% by volume.

Particular examples for preferred anti-oxidant stabilizers oranti-oxidant agents are pharmacologically acceptable substances, able toinhibit the degradation of Hyperforin and/or to reduce oxidants in theextract or the pharmaceutical composition. Particular examples areorganic thiol compounds, such as cysteine and glutathione, as well asascorbic acid and derivates thereof such as the fatty acid esters ofascorbic acid, such as the myristate, palmitate and stearate.

The anti-oxidant stabilizers are added to the extract preparation ofHypericum in an amount sufficient to stabilize the Hyperforin. Ingeneral concentrations from 0.01 to 5% anti-oxidant stabilizer based onthe extract of Hypericum are sufficient.

In a further embodiment it will be proceeded as described above but theaddition of the stabilizer is carried out at the stage after drying theextract solution, i.e. after stripping off the solvent.

In a further preferred embodiment of the invention the anti-oxidantstabilizer is added, at the stage of the finished pharmaceuticalproduct, together with other pharmaceutical additives.

Preferably all embodiments are carried out under the exclusion of lightand oxygen.

The obtained extracts can be processed together with conventionalpharmaceutical additives, optionally after adding again a stabilzer topharmaceutical compositions, such as capsules, film tablets and coatedtablets.

Pharmaceutical additives are fillers, binding agents, disintegrants,lubricants and coating agents for film tablets and coated tablets, aswell as oils and fats as fillers for soft gelatin capsules.

The present invention is explained by means of the following examples.Percentages are percents by weight if not otherwise stated. Nitrogen wasused as an inert gas (protective gas). It should be noted that alsoother inert gases, such as argon or krypton can be used.

EXAMPLE 1 (COMPARISON EXAMPLE)

1 kg crude herbal drug of St. John's wort was finely milled in a milland 7 kg 70(v/v)% ethanol was added. The suspension of 1 kg crude herbaldrug and 7 kg solvent was intensively stirred at 55° C. for one hourunder inert gas. Then the resulting extract was separated from the crudeherbal drug by means of centrifugation. The residue of the drug wasaccordingly extracted for a second time with 7 kg solvent. The twoextract solutions were combined and the dry residue in the extract wasdetermined with an aliquot. The extract was gently concentrated underreduced pressure to a dry residue content of 72% and again dried at 40°C. under reduced pressure. 0.44 kg dry extract was obtained. TheHyperforin content was 0.37%.

EXAMPLE 2

8 kg crude herbal drug of St. John's wort was finely milled in a milland 56 kg 70(v/v)% ethanol was added. The oxygen content of the usedsolvent was reduced before by means of rinsing with inert gas. Thesuspension of 8 kg crude herbal drug and 56 kg solvent was intensivelystirred under inert gas at 55° C. for one hour. Then the obtainedextract was separated from the drug by means of centrifugation whilerinsing with nitrogen as an inert gas. The drug residue was extracted asecond time in the same manner. The two extract solutions were combinedand 0.1% ascorbic acid was added. The solution was intensively stirredfor 10 minutes under nitrogen as inert gas and was then gentlyconcentrated under reduced pressure to a dry residue content of 70% andagain dried at 40° C. under reduced pressure. 2.52 kg stabilized dryextract with a Hyperforin content of 0.9% was obtained.

EXAMPLE 3

To 400 g dry, finely milled fresh St. John's wort 3.2 kg n-heptane wereadded. 12 mg ascorbic acid palmitate were added and the mixture was thenextracted during one hour by permanent stirring at 50° C. underexclusion of light. Then the mixture was sucked off by means of a SeitzSupra 1500 Filter and the drug residue was extracted a second time inthe same manner. The combined extract solutions were concentrated at 35°C. by means of a rotary evaporator under exclusion of light to a dryresidue content of about 70% and than freeze-dried. 21 g dry extract wasobtained with a Hyperforin content of 1.7%.

EXAMPLE 4

To 470 g dry, finely milled St. John's wort 15 mg of ascorbic acidpalmitate were added and then the mixture was delivered into ahigh-pressure-extraction unit and extracted under 200 bar at 35° C.About 7.5 kg carbon dioxide was used. After the extraction, the pressurewas reduced to 60 bar in order to separate the extract. The extract wasremoved from the unit and mixed with 10 mg ascorbic acid palmitate. 12.2g dry extract with a Hyperforin content of 1.9% was obtained.

EXAMPLE 5

2.4 kg crude herbal drug of St. John's wort was milled in a mill and 16kg 80(v/v)% methanol was added, which was rinsed with nitrogen before.This mixture was then stirred for one hour at 55° C. The obtainedextract solution was separated from the drug residue by means ofcentrifugation. The residue of the drug was accordingly extracted for asecond time. The two extract solutions were combined and 1.0% by weightascorbic acid was added. This solution was stirred for 15 minutes. Thenthe extract solution was gently concentrated under reduced pressure to adry residue content of 70% and then again dried at 40° C. under reducedpressure. 0.5 kg stabilized dry extract with a Hyperforin content of0.7% was obtained. The content of total Hypericin in this extract was0.46%.

EXAMPLE 6

Checking the stability of Hyperforin.

In this example the Hyperforin content of an extract according toExample 1 without particular precautionary measures and additions duringthe preparation was compared with extracts prepared according toExamples 2 to 5 of this invention. The extracts prepared in accordancewith the present invention were stored under nitrogen and exclusion oflight at room temperature. The results are summerized in Table I. Theresult shows a substantially unchanged Hyperforin content of theextracts prepared in accordance with the present invention after 6months.

dry extract hyperforin hyperforin content % Example Initial content %after 13 weeks after 6 months Example 1 0.37 0.0 0.0 Example 2 0.9 0.90.88 Example 3 1.7 1.7 1.68 Example 4 1.9 1.9 1.89 Example 5 0.7 0.70.63

EXAMPLE 7

Soft-gelatine capsules with an extract of Hypericum.

Composition: dry extract of Hypericum 300 mg ascorbic acid 0.25 mgoctyldodecanol 200 mg

Preparation:

The dry extract and ascorbic acid were dispersed together inoctyldodecanol and processed under exclusion of atmospheric oxygen tosoft-gelatine capsules.

EXAMPLE 8

Film tablet with extract of Hypericum.

Composition: dry extract of Hypericum 300 mg cellulose 100 mg modifiedstarch 90 mg Na-carboxymethylcellulose 30 mg highly dispersedsiliciumdioxide 5.0 mg ascorbic acid 5.0 mg magnesium stearate 5.0 mghydroxypropylmethylcellulose-coating 20.0 mg

Preparation:

The components were mixed in dry condition in a mixer and were directlypressed into tablets. The obtained tablets were coated with a coating ofhydroxypropylmethylcellulose.

What is claimed is:
 1. A stable extract of Hypericum perforatum L. (St.John's wort) with a Hyperforin content of 0.1% to 2%, wherein theextract comprises an amount of a stabilizer selected from the groupconsisting of organic thiol compounds, ascorbic acid, ascorbic acidderivatives, and mixtures thereof effective to stabilize the Hyperforinagainst decomposition or degradation.
 2. An extract according to claim1, wherein the stabilizer is present in a concentration of 0.01% to 5%,based on the extract.
 3. An extract according to claim 1, wherein thestabilizer is present in a concentration of 0.2% to 1%, based on theextract.
 4. An extract according to claim 1, wherein the stabilizer iscysteine.
 5. An extract according to claim 1, wherein the stabilizer isglutathione.
 6. An extract according to claim 1, wherein the stabilizeris ascorbic acid.
 7. An extract according to claim 1, wherein thestabilizer is a fatty acid ester of ascorbic acid.
 8. In a process forthe preparation of a stable extract containing about 0.1% to 2%Hyperforin wherein Hypericum perforatum L. plant material is extractedwith pharmaceutical inorganic or organic solvents or mixtures thereof,with the proviso that the solvents are not oily extraction agents, theimprovement comprising adding a stabilizer selected from the groupconsisting of organic thiol compounds, ascorbic acid and derivativesthereof, either during or after the preparation of the extract, in anamount sufficient to stabilize the Hyperforin.
 9. A Process according toclaim 8, wherein the plant material is fresh plant material.
 10. AProcess according to claim 8, wherein the plant material is dried plantmaterial.
 11. A Process according to claim 8, wherein the stabilizer iscysteine.
 12. A Process according to claim 8, wherein the stabilizer isglutathione.
 13. A Process according to claim 8, wherein the stabilizeris asorbic acid.
 14. A Process according to claim 8, wherein thestabilizer is a fatty acid ester of ascorbic acid.
 15. A Processaccording to claim 8, wherein the stabilizer is added in a concentrationof 0.01% to 5%, based on the extract.
 16. A Process according to claim8, wherein a solvent is used for the extraction.
 17. A Process accordingto claim 8, wherein the solvent used for extraction is selected from thegroup consisting of aqueous ethanol, aqueous methanol, alkanes havingabout 5-8 carbon atoms, liquid carbon dioxide and supercritical carbondioxide.
 18. A Process according to claim 8, wherein the stabilizer isadded after drying the extract solution.
 19. A Process according toclaim 8, wherein the stabilizer is added only to the dry extracttogether with conventional pharmaceutical additives.
 20. A Processaccording to claim 8, wherein the process is carried out in the absenceof light.
 21. A pharmaceutical composition containing an extractaccording to claim 1 and conventional pharmaceutical additives for thetreatment of depression and psychovegetative disorders.
 22. The processaccording to claim 8, wherein the stabilizer is added in a concentrationof 0.2% to 1% based on the extract.
 23. The process according to claim8, wherein the process is carried out in the absence of oxygen.
 24. Theprocess according to claim 8, wherein the process is carried out in theabsence of light and oxygen.
 25. A stable composition comprising (a)Hyperforin extracted from Hypericum perforatum L. using water andmethanol or ethanol, the amount of hyperforin being from about 0.1% to2%; and (b) an amount of a stabilizer selected from the group consistingof of organic thiol compounds, ascorbic acid, ascorbic acid derivatives,and mixtures thereof effective to stabilize the Hyperforin againstdecomposition or degradation.
 26. A plant extract comprising (a) about0.1% to 2% of hyperforin; and (b) an amount of a stabilizer selectedfrom the group consisting of of organic thiol compounds, ascorbic acid,ascorbic acid derivatives, and mixtures thereof effective to stabilizethe Hyperforin against decomposition or degradation, the hyperforinbeing stable in the composition for at least 12 months.
 27. Apharmaceutical composition containing an extract according to claim 2and conventional pharmaceutical additives for the treatment ofdepression and psychovegetative disorders.
 28. A pharmaceuticalcomposition containing an extract according to claim 3 and conventionalpharmaceutical additives for the treatment of depression andpsychovegetative disorders.
 29. A pharmaceutical composition containingan extract according to claim 4 and conventional pharmaceuticaladditives for the treatment of depression and psychovegetativedisorders.
 30. A pharmaceutical composition containing an extractaccording to claim 6 and conventional pharmaceutical additives for thetreatment of depression and psychovegetative disorders.
 31. Apharmaceutical composition containing an extract according to claim 7and conventional pharmaceutical additives for the treatment ofdepression and psychovegetative disorders.